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On Apple's iMac page, it says:

Configurable to 8GB (all models) or 16GB (select models)

However both Apple's iMac: How to remove or install memory page and indicate that all of the 2011 iMac models are configurable to 16 GB. Does the above quote simply mean than select models are only configurable to 16 GB on the Apple online store? If I buy the $1200 iMac (MC309LL/A), I should be able to install 16 GB of RAM bought separately from Crucial, correct?

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What's ever worse is that the manuals for the iMacs say (incorrectly) that they all have 4 RAM slots. In fact, the model you mention has only two slots on the logic board. – bmike Oct 31 '11 at 20:21
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Correct. You may even upgrade it to 32GB.

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The iMac MC309LL/A has only two RAM slots. I know of no reputable vendor that has said a pair of 16 GB RAM will work to take that model to 32 GB. Have you actually tried a chip of that sizing? A pair of 8 works well as we tested some today on that exact model. – bmike Oct 31 '11 at 20:15
Why do so many sites (even Apple's own support page) claim it supports 16 GB and that it has 4 slots - have you personally seen that the latest MC309LL/A has only 2 memory slots? – Jake Petroules Oct 31 '11 at 22:56

Apple offers CTO and will let you fill your iMac (Late 2011) with RAM modules sized at 2 GB and 4 GB each.

From Apple, the entry level MC309LL/A has two RAM slots so you can take it to 8 GB (2 x 4 GB SO-DIMM) but many reputable vendors are selling 8 GB modules that seem to work well and without issue on that hardware - 16 GB (2 x 8 GB SO-DIMM).

The rest of the Late 2011 iMacs have 4 RAM slots, so you can take them to 32 GB (4 x 8 GB SO-DIMM) even though Apple intends / configures / supports / recommends a max of 16 GB (4 x 4 GB SO-DIMM) for the rest of the lineup.

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Just a nitpick, but computers in general (including Macs) do not take ram "Chips", they take RAM modules, or (colloquially) sticks. The RAM module has chips on it, but calling the whole thing a chip is akin to referring to an entire car as an engine or tire. – Fake Name Oct 31 '11 at 23:16

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